1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method, and more particularly to a substrate processing apparatus and a substrate processing method for use in polishing a substrate, such as a semiconductor wafer, to provide a planarized surface of the substrate.
The present invention also relates to a substrate holding mechanism and a substrate holding method, and more particularly to a substrate holding mechanism suitable for use in a cleaning apparatus and a drying apparatus for a substrate such as a semiconductor wafer.
The present invention also relates to units and several types of components and mechanisms for use in a substrate processing apparatus.
2. Description of the Related Art
The trend of a semiconductor device in recent years has been a highly integrated structure, which entails finer interconnects of a circuit and a smaller distance between the interconnects. In fabrication of the semiconductor device, many kinds of materials are deposited in a shape of film on a silicon wafer repeatedly to form a multilayer structure. It is important for forming the multilayer structure to planarize a surface of a wafer. A polishing apparatus for performing chemical mechanical polishing (CMP) is typically used as one technique of planarizing the surface of the wafer. This type of apparatus is often called a chemical mechanical polishing apparatus.
This chemical mechanical polishing (CMP) apparatus typically includes a polishing table supporting a polishing pad thereon, a top ring for holding a wafer, and a nozzle for supplying a polishing liquid onto the polishing pad. When polishing a wafer, the top ring presses the wafer against the polishing pad, while the polishing liquid is supplied onto the polishing pad. In this state, the top ring and the polishing table are moved relative to each other, whereby the wafer is polished to have a planarized surface.
A substrate processing apparatus is an apparatus which has, in addition to the CMP apparatus, functions of cleaning the polished wafer and drying the cleaned wafer. In this substrate processing apparatus, there is a need to improve a throughput in substrate processing. Since the substrate processing apparatus has a variety of processing sections including a polishing section and a cleaning section, a processing delay in each processing section results in a decrease in the throughput of the substrate processing apparatus in its entirety. For example, in a conventional substrate processing apparatus, only a single cleaning line is provided, while plural polishing units are provided. Consequently, plural polished wafers cannot be cleaned and dried simultaneously. Moreover, of plural processes on the cleaning line (e.g., a primary cleaning process, a secondary cleaning process, and a drying process), the slowest process becomes a rate-limiting step in all processes and thus decides a processing time (i.e., throughput) of all processes.
The throughput of the substrate processing apparatus in its entirety can be affected not only by the processing sections, such as the polishing section and the cleaning section, but also by a transfer mechanism for transferring a wafer. Further, wafer transferring operations between the top ring and the transfer mechanism can also affect the overall throughput. In this manner, the throughput of the substrate processing apparatus as a whole depends on a variety of processing operations and transferring operations.
For example, the substrate processing apparatus has a linear transporter for transferring a wafer between polishing units. This linear transporter moves the wafer linearly in a horizontal direction to thereby transfer the wafer to a wafer-transfer position in each polishing unit. Then, the wafer is pushed upward to the top ring by a pusher which is provided separately from the linear transporter. In this manner, since the horizontal movement and the vertical movement of the wafer are performed by the linear transporter and the pusher separately, a long time is needed in transferring the wafer.
The pusher is provided in the wafer-transfer position for each polishing unit. In addition, each pusher needs an XY stage for fine adjustment of the wafer-transfer position between the top ring and the pusher. Consequently, the wafer transfer mechanism has complicated structure as a whole and entails a lot of accompanying wires and pipes to be provided. Moreover, if the transfer mechanism breaks down, it is necessary to access the wafer-transfer position for repair, and this can make it difficult to restore the transfer mechanism.
A long downtime of the substrate processing apparatus as a result of a failure and maintenance thereof leads to an increase in cost for processing a wafer. For this reason, easy maintenance has recently been required for the substrate processing apparatus. It is also required to reduce components of the substrate processing apparatus to simplify the structure thereof and to achieve a lower cost.
For example, the top ring swings between a polishing position above the polishing pad and the wafer-transfer position. Accordingly, a swinging mechanism for the top ring requires a regular maintenance. This swinging mechanism includes bearings for supporting a swing shaft of the top ring, a motor and reduction gears for driving the swing shaft. A top ring head, which supports the top ring, is mounted on an upper end of the relatively long swing shaft, and the reduction gears and the motor are coupled to a lower end of the swing shaft. A bearing case is arranged around the bearings. This bearing case extends through a polisher pan which partitions a polishing room and a lower room below the polishing room. Further, the bearing case is located below the polisher pan. A top ring assembly, including the top ring and the top ring head, is relatively long and heavy. Therefore, the top ring assembly may present disadvantages in maintenance thereof.
In the conventional substrate processing apparatus, a pressure adjuster for adjusting a pressing force of the top ring against a substrate is provided outside the top ring head. This arrangement entails a long distance between the pressure adjuster and the top ring and may cause a delay in an actual change in the pressing force in response to a command for changing the pressing force against the substrate.
Pure water is used for cleaning a top ring and a dresser provided in each of the polishing units of the substrate processing apparatus. In a conventional structure, the pure water is supplied from a single header to the polishing units through plural pipes. This structure may present a problem that a flow rate of the pure water in one polishing unit becomes unstable as a result of use of the pure water in the other.
In the fabrication processes of the semiconductor device, cleaning and drying of a substrate (e.g., a semiconductor wafer) are performed after a polishing process and a plating process. For example, in cleaning of the substrate, a substrate holding mechanism holds the substrate and rotates the substrate. In this state, a cleaning liquid is supplied onto the substrate. A mechanism having an actuator for driving chucks so as to hold the substrate is known as a conventional substrate holding mechanism.